Along with an increased storage capacity of personal computers and an improved audio playback technique, the number of users who record music data in personal computers and play it back is increasing.
When many pieces of music data are recorded, they are classified into a plurality of folders, as shown in FIG. 1, according to, for example, the category, the artist, or the album, and a plurality of levels of classification are further provided so as to construct a hierarchical structure. This enables the user to search for a desired piece of music.
If a plurality of pieces of music data are not classified in a hierarchical structure by using folders unlike the example shown in FIG. 1, it is very difficult for the user to select a desired piece from all the pieces of music data. If, for example, the user remembers the file name (such as the name of the song) of a music data file and desires to listen to it, the user can search for the file name. However, if the user does not know the name of a song even if the user remembers the name of a composer, or if the user desires to listen to the performance of a certain orchestra, the user is unable to find the desired piece of music data unless a plurality of pieces of music data are classified in a hierarchical structure, as shown in FIG. 1, that is, a roughly classified folder, i.e., “classic”, is further classified into intermediate folders, such as “by composer” and “by orchestra”, and folders by composer and folders by orchestra are further provided for the intermediate folders “by composer” and “by orchestra”.
When the user has found the desired piece of music data by tracing the hierarchical structure, the user is able to play it back to enjoy it by performing, for example, a click operation on an icon indicating the desired piece of music data.
If the music data is copy-protected, it can be copied to a removable disk, such as a CD-R, within a preset number of copies. The user is able to search a folder structure, such as that shown in FIG. 1, for a desired piece of music data, and copy it to a removable disk so as to enjoy it in a room away from a personal computer.
However, when music data is sorted out in a hierarchical structure shown in FIG. 1, if, for example, the user desires to play back a music piece A, a complicated operation is required, i.e., the “by composer” folder is selected from the “classic” folder, then, a “composer B” folder is opened from the “by composer” folder, and finally, the music piece A is selected.
Also, if the music piece A is performed by “C orchestra”, the user is unable to search for the music piece A by using the “by orchestra” folder unless data of the music piece A is contained in the “C orchestra” folder, which is a category different from the “composer B”. Accordingly, it is necessary to record the same data in a plurality of folders, thereby wasting a limited storage capacity.
In a complicated hierarchical structure, it is very difficult for the user to know the level of the structure to which a folder currently referred by the user belongs. For example, if the user traces an incorrect level to search for a certain piece of music, it is sometimes necessary to return to the previous level depending on the file system.
When a data file of a certain piece of music is selected and a playback operation is performed after tracing such a complicated hierarchical structure, the music is played back from the beginning. Even if the user listens to only the first portion of music (i.e., the introduction in many pieces of pop music), it is difficult to determine whether the music which is currently played back is the music desired by the user. If the music played back is not the music desired by the user, the user has to trace the complicated hierarchical structure again to search for the desired piece of music.
From another point of view, since music data is precisely classified into folders, the user has to trace the folders in a hierarchical structure to reach the bottommost level in order to play back the music data. That is, it is necessary that the user understands the database structure to a certain degree, and consciously selects a music data file to perform a playback operation. Accordingly, when the user desires to casually listen to music as BGM (BackGround Music), for example, when the user listens to radio broadcasting, the user may feel it is a nuisance to trace a hierarchical structure.
In radio broadcasting, it is possible to listen to a program to one's taste of a broadcast station to one's taste, and it is also possible to find a new piece of music to one's taste while unknown music is on. When the user has to select a piece of music to be played back, even if unknown music data is recorded in a user's personal computer, it is difficult to select only unknown pieces from many pieces of music data.
If the user desires to enjoy music in a room away from the personal computer, it is necessary to copy music data on a removable disk. Then, if a home network is constructed in a household to record music data in a server and to allow a client to play it back, it is difficult for the user to easily perform the operation unless the user understands the configuration of a client-server system to a certain degree and also understands the hierarchical structure of the music data recorded in the server to a certain degree.